Block Diagrams

Audio System | Radio System | Power Supply System | Feedback Control System

Block diagrams are used to understand (and design) complete circuits by breaking them down into smaller sections or blocks. Each block performs a particular function and the block diagram shows how they are connected together. No attempt is made to show the components used within a block, only the inputs and outputs are shown. This way of looking at circuits is called the systems approach.

Power supply (or battery) connections are usually not shown on block diagrams.

Audio Amplifier System

The power supply (not shown) is connected to the pre-amplifier and power amplifier blocks.

Microphone - a transducer which converts sound to voltage.
Pre-Amplifier - amplifies the small audio signal (voltage) from the microphone.
Tone and Volume Controls - adjust the nature of the audio signal.
The tone control adjusts the balance of high and low frequencies.
The volume control adjusts the strength of the signal.
Power Amplifier - increases the strength (power) of the audio signal.
Loudspeaker - a transducer which converts the audio signal to sound.

Radio Receiver System

The power supply (not shown) is connected to the audio amplifier block.

Aerial - picks up radio signals from many stations.
Tuner - selects the signal from just one radio station.
Detector - extracts the audio signal carried by the radio signal.
Audio Amplifier - increases the strength (power) of the audio signal.
This could be broken down into the blocks like the Audio Amplifier System shown above.
Loudspeaker - a transducer which converts the audio signal to sound.

Regulated Power Supply System

Transformer - steps down 230V AC mains to low voltage AC.
Rectifier - converts AC to DC, but the DC output is varying.
Smoothing - smooths the DC from varying greatly to a small ripple.
Regulator - eliminates ripple by setting DC output to a fixed voltage.

For futher information please see the Power Supplies page.

Feedback Control System

The power supply (not shown) is connected to the control circuit block.

Sensor - a transducer which converts the state of the controlled quantity to an electrical signal.
Selector (control input) - selects the desired state of the output. Usually it is a variable resistor.
Control Circuit - compares the desired state (control input) with the actual state (sensor) of the controlled quantity and sends an appropriate signal to the output transducer.
Output Transducer - converts the electrical signal to the controlled quantity.
Controlled Quantity - usually not an electrical quantity, e.g. motor speed.
Feedback Path - usually not electrical, the Sensor detects the state of the controlled quantity.

Next Page: Circuit Diagrams | Studying Electronics